With growing interest in the hydrogen energy systems, research and development of the hydrogen storage materials have been actively conducted searching for materials for use in storage and transport of hydrogen, separation and refinement of hydrogen gas, energy conversion apparatuses, and the like. The research and development has shown that the hydrogen storage materials subjected to repeated hydrogen absorption and desorption are pulverized in a crumbling manner. Thus, materials having excellent hydrogen storage capability and also being highly resistant to pulverization resulting from the repeated absorption and desorption of hydrogen have been strongly demanded. In response to this, a proposal has been made to recommend a material having a thin-film laminated structure formed from a group 4A metal and any one of the group 6A, 7A and 8A metals (Japanese Laid-Open Publication No. 9-59001). Such a laminated, thin film body has a highly increased resistance to pulverization resulting from absorption and desorption of hydrogen. Moreover, since the group 4A metals having an hcp structure in the state of a bulk material have a bcc structure in the thin-film, laminated structure, the number of interstitial sites that may store hydrogen is increased. Since the group 4A metals originally have strong bonding power with hydrogen and thus have high hydrogen absorbing capability, the increased interstitial site density results in increased hydrogen storage capability. Accordingly, materials being less susceptible to pulverization and having extremely high hydrogen storage capability can be obtained from the above-mentioned material having a thin-film, laminated structure formed from a group 4A metal and any one of the group 6A, 7A and 8A metals.
However, the above-mentioned thin-film, laminated material includes a group 4A element, Ti, and therefore is heavy in weight. Moreover, mass production of the thin-film, laminated material is restricted in terms of resources, thereby necessarily making the material highly expensive beyond the price suitable for practical use, as an industrial material of this type. Accordingly, an element alternative to the group 4A metals had been sought. As a result, it was found that the group 2A and 3A metals have the capability similar to that of the group 4A metals in terms of the hydrogen storage capability, and a hydrogen storage laminated material was proposed which has a group 2A or 3A metal substituted for a group 4A metal (Japanese Patent Application No. 11-165890). For example, Mg of the group 2A elements is rich in resources and also light in weight. Therefore, it has become possible to obtain an inexpensive, lightweight laminated material being less susceptible to pulverization and also having excellent hydrogen storage capability.
It is an object of the present invention to provide a hydrogen storage material having high hydrogen storage capability and also having such a low hydrogen desorption temperature as not to significantly hinder the daily, easy use of the nickel-hydrogen secondary batteries, hydrogen-utilizing fuel cells, hydrogen-utilizing energy conversion systems and the like, and more specifically, as low as 150.degree. C. or less, and capable of being mass-produced, and a manufacturing method of the same.